Tension-based non-pneumatic tire

ABSTRACT

A non-pneumatic tire for supporting a load by working in tension comprising a generally annular inner surface, a generally annular outer ring, and an interconnected web having a plurality of web elements and comprising a plurality of generally polygonal openings. Web elements are sized, oriented and comprised of a material that facilitates buckling when subjected to a compressive load. By buckling, those elements in a deformed portion of the tire between a hub and a footprint region where the tire contacts a surface may assume a significantly reduced portion of the load, if any. This causes web elements in other portions of the interconnected web to operate in tension to support the load. With the portion of the tire in the footprint region not bearing a significant portion of the load, non-pneumatic tire may exhibit a more comfortable ride subject to less noise and vibration and improved handling capabilities.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of U.S. application Ser. No.11/691,968 filed on Mar. 27, 2007, and issued as U.S. Pat. No. 8,104,524on Jan. 31, 2013, the complete disclosures of which are expresslyincorporated by reference herein in their entirety.

This invention was made, in part, with United States government supportawarded by the United States Army Research Laboratory under grant numberW911NF-06-2-0021. Accordingly, the United States may have certain rightsin this invention.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to a non-pneumatic tire (NPT) orcombination of a tire and hub that supports an applied load by workingin tension and is capable of serving as a replacement for pneumatictires and an improvement over other forms of non-pneumatic tires.

2. Description of the Related Art

Non-pneumatic, or airless, tires have historically been comprisedlargely of an entirely solid substance. These solid tires made the riderather uncomfortable for passengers and caused greater damage to thesuspension of a vehicle, which had to compensate for their lack of“give.” Eventually, it was found that putting pressurized air in tirescreated a more comfortable ride. However, along with their advantages,pneumatic tires still possess some drawbacks.

The material that encloses standard pneumatic tires is susceptible toleaking the pressurized air it tries to withhold. This occurs both vialeakage around the wheel rim, and on a smaller scale, when the rubber ofthe tire absorbs the oxygen. As a result, loss of pressure causes thetire to flatten in the area where the load is applied, subjecting alarger portion of the tire to the load with every revolution, leading toquicker degradation of the tire. Furthermore, a tire reliant uponpressurized air is susceptible to being punctured leading to rapidrelease of the pressurized air.

Focusing on fuel efficiency, safety and ride comfort, several attemptshave been made to address the problems associated with pneumatic tireswhile retaining their advantages over solid non-pneumatic tires. By wayof example, U.S. Published Application 2006/0113016 by Cron, et al, andassigned to Michelin, discloses a non-pneumatic tire that itcommercially refers to as the Tweel™. In the Tweel™, the tire combineswith the wheel. It is made up of four parts that are eventually bondedtogether: the hub, a spoke section, a reinforced annular band thatsurrounds the spoke section, and a rubber tread portion that contactsthe ground.

Other alternatives to standard non-pneumatic tires have been attempted,including making solid tires out of polyurethane instead of rubber andsuspending reinforcement materials within the polyurethane duringmolding. Another alternative is to use internal ribs made of athermoplastic that are subsequently reinforced with glass fibers. Athird alternative is to use an electroactive polymer that is capable ofchanging shape when an electrical current is applied. This allows thetire to change shape or size based upon road conditions by using theautomobile's electrical system.

BRIEF SUMMARY OF THE INVENTION

A novel non-pneumatic tire for supporting an applied load is provided,the tire having an inner surface that attaches to a hub or wheel havingan axis of rotation, an outer ring, and an interconnected web betweenthe inner surface and the outer ring. The interconnected web is made ofa material that is relatively stronger in tension than in compressionsuch that the portion of the web between the hub and a footprint regionmay either buckle or be subject to a significantly smaller portion ofthe load, if any, while the rest of the load may be distributed throughthe remaining portion of the interconnected web. In one embodiment, theinterconnected web may attach directly to the hub or tread-carryinglayer.

The interconnected web may be one of multiple possible forms. In oneembodiment, the elements of the web form multiple layers of interfittinggenerally polygonal openings such that there are at least two adjacentlayers of openings spaced at different radial distances from each otherwhen viewed at any radial slice of the web. The openings of one layermay be similarly shaped compared to the openings of at least one otherlayer, but they may also be shaped differently. In addition, theopenings of one layer may or may not be similarly shaped to the otheropenings in that same layer. Furthermore, while the openings of onelayer may be similarly shaped to the openings of another layer, they maybe sized differently, such that the openings of a radially outer layermay be larger or smaller than the openings of a comparatively radiallyinner layer.

A major advantage of using a non-pneumatic tire compared to a standardtire is eliminating flat tires. If a portion of the web is compromised,the load will be redistributed through other elements of the web byvirtue of the fact that the web is interconnected, prolonging the lifeof the tire. In addition, by not carrying any significant load along afootprint region where the tire contacts a surface, a smoother rideresults since the non-pneumatic tire is less susceptible to shock andvibration.

These and other features and advantages are evident from the followingdescription of the present invention, with reference to the accompanyingdrawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a front view of an undeformed non-pneumatic tire.

FIG. 2 is a front view of the non-pneumatic tire of FIG. 1 beingdeformed when subjected to a load.

FIG. 3 is a sectional perspective view of the undeformed non-pneumatictire taken along line 3-3 in FIG. 1.

FIG. 4 is a front view of another embodiment of an undeformednon-pneumatic tire.

FIG. 5 is a front view of still another embodiment of an undeformednon-pneumatic tire.

FIG. 6 is a front view of a further embodiment of an undeformednon-pneumatic tire.

FIG. 7 is a front view of yet another embodiment of an undeformednon-pneumatic tire.

FIG. 8 is a front view of another embodiment of an undeformednon-pneumatic tire.

FIG. 9 is a front view of still another embodiment of an undeformednon-pneumatic tire.

FIG. 10 is a front view of a further embodiment of an undeformednon-pneumatic tire.

FIG. 11 is a sectional view of a prior art tread-carrying portionattached to a non-pneumatic tire taken along line 11-11 in FIG. 2.

FIG. 12 is a sectional view of another tread-carrying portion attachedto a non-pneumatic tire taken along line 11-11 in FIG. 2.

FIG. 13 is a sectional view of still another tread-carrying portionattached to a non-pneumatic tire taken along line 11-11 in FIG. 2.

FIG. 14 is a perspective view of an embodiment of an undeformednon-pneumatic tire with circumferentially offset segments.

FIG. 15 is a sectional perspective view of the undeformed non-pneumatictire taken along line 15-15 in FIG. 14.

FIG. 16 is a sectional view of the undeformed non-pneumatic tire takenalong line 16-16 in FIG. 14.

FIG. 17 is a perspective view of the nonpneumatic tire of FIG. 1.

FIG. 18 is an enlarged, cutaway view of the interconnected web of thenonpneumatic tire of FIG. 17.

FIG. 19 is a graphical comparison of the relative stresses in theinventive tension-based non-pneumatic tire vs. the percentage of thetire experiencing that stress compared to another tension-basednon-pneumatic tire.

FIG. 20 is a graphical comparison of the relative strains in theinventive tension-based non-pneumatic tire vs. the percentage of thetire experiencing that strain compared to another tension-basednon-pneumatic tire.

DETAILED DESCRIPTION OF THE INVENTION Benefits Over TraditionalPneumatic Tires

A non-pneumatic tire 10 may exhibit many of the same performancecharacteristics as traditional pneumatic tires. It demonstrates ageneral ride quality and traction similar to current pneumatic tires. Itmay also have costs, weight, load supporting capability and tread lifesimilar to current pneumatic tires.

However, the non-pneumatic tire of the present invention demonstratesseveral advantages over standard pneumatic tires. In addition tovirtually eliminating blowouts and flat tires, the ability of agenerally annular outer ring 30 and an interconnected web 40 to deformin an area around footprint region 32 as shown in FIG. 2 reduces thestresses placed on hub 60 when hitting a bump, pothole, or similarobstacle, thereby making non-pneumatic tire 10 and hub 60 lesssusceptible to damage. Without relying on air pressure to maintain itsfunctionality, interconnected web 40 of non-pneumatic tire 10 may alsobe better able to withstand damage caused by projectiles. If a portionof interconnected web 40 is damaged, a load, L, which is generallyapplied perpendicular to axis of rotation 12, may be transferred to theremaining elements so that a vehicle relying on non-pneumatic tires 10is not immediately disabled. In addition, because non-pneumatic tire 10cannot be over- or under-inflated, footprint region 32 may remaingenerally constant, improving fuel efficiency as compared to traditionalpneumatic tires.

Generally annular outer ring 30 combined with interconnected web 40 maydisplay higher lateral stiffness compared to standard pneumatic tires,especially in the embodiment in which tread-carrying layer 70 isattached. Therefore, while general ride quality may be similar tostandard pneumatic tires, non-pneumatic tire 10 may achieve improvedcornering ability. Non-pneumatic tire 10 may also require lessmaintenance by obviating the need to check and maintain air pressure.

Benefits Over Prior Non-Pneumatic Tires

Besides its benefits over traditional pneumatic tires, non-pneumatictire 10 may exhibit multiple advantages over other non-pneumatic tires.Most of these other tires have a solid rim and a solid tire section andare in production for low-speed applications. In comparison to thesetires, non-pneumatic tire 10 may be significantly lighter.Interconnected web 40 may allow non-pneumatic tire 10 to absorb impactssignificantly better, resulting in a more comfortable ride. In addition,other non-pneumatic tires are not usable at high speeds due to theamount of vibration that is generated.

Some conventional non-pneumatic tires work by placing the portion of thetire that is between the applied load and the contact surface incompression. This causes that section of the tire and its internalstructure to deform under the load. When the body to which the tire isattached is not in motion, this portion of the tire remains deformedunder the static load. Over time, this can lead to semi-permanentdeformation of the tire causing decreased performance, increased noiseand vibration and worse fuel efficiency, among other things. Incontrast, buckled section 48 carries very little, if any, load so tiremay remain statically deformed for a while and not experience anyappreciable semi-permanent deformation.

Benefits Over Other Tension-Based Non-Pneumatic Tires

In comparison to other tension-based non-pneumatic tires, tire 10 of thecurrent invention may demonstrate even further benefits. Non-pneumatictire 10 may experience smaller stresses and strains under similarloading conditions than other tension-based non-pneumatic tires, as canbe seen in FIGS. 19 & 20. By allowing air to flow through the tire 10and around web elements 42, the design of interconnected web 40 mayresult in less heat generation as well as less fatigue, prolonging thelife of tire 10. The ability of interconnected web 40 to buckle aroundfootprint region 32, thereby causing less reactive force when passingover an obstacle, may also result in less vibration and a better ride.Despite the ability of interconnected web 40 to buckle, it may also berelatively stiff when compared to the internal structure of othertension-based non-pneumatic tires. This may result in less noise beinggenerated, resulting in a quieter ride. It may also cause non-pneumatictire 10 to experience better starting and stopping performance.

Generally Annular Inner Surface

Non-pneumatic tire 10 comprises a generally annular inner surface 20that engages a hub 60 to which tire 10 is mounted. Hub 60 has an axis ofrotation 12 about which tire 10 spins. Generally annular inner surface20 has an internal surface 23 and an external surface 24 and may be madeof cross-linked or uncross-linked polymers. More specifically, generallyannular inner surface may be made of a thermoplastic material such as athermoplastic elastomer, a thermoplastic urethane or a thermoplasticvulcanizate. Still more specifically, generally annular inner surface 20may be made of rubber, polyurethane, or some other material. In thisapplication, the term “polymer” means cross-linked or uncross-linkedpolymers.

For smaller applied loads, L, generally annular inner surface 20 may beadhesively engaged with hub 60 or may undergo some chemical structurechange allowing it to bond to hub 60. For larger applied loads, L,generally annular inner surface 20 may be designed in a manner thatallows it to engage hub 60 via some form of a mechanical connection suchas a mating fit, although a mechanical connection may be used forsupporting smaller loads as well.

This allows both hub 60 and generally annular inner surface 20 the extrastrength to support the larger applied load, L. In addition, amechanical connection has the added benefit of ease ofinterchangeability. If non-pneumatic tire 10 needs to be replaced,generally annular inner surface 20 can be detached from hub 60 andreplaced. Hub 60 may then be remounted to the axle of the vehicle,allowing hub 60 to be reusable.

Generally Annular Outer Ring

Non-pneumatic tire 10 further comprises generally annular outer ring 30surrounding interconnected web 40 (discussed below). Outer ring 30 maybe designed to deform in an area around and including footprint region32, which decreases vibration and increases ride comfort. However, sincenon-pneumatic tire may not have a sidewall, generally annular outer ring30, combined with interconnected web 40, may also add lateral stiffnessto tire 10 so that tire 10 does not unacceptably deform in portions awayfrom footprint region 32.

In one embodiment, generally annular inner surface 20 and generallyannular outer ring 30 are made of the same material as interconnectedweb 40. Generally annular inner surface 20 and generally annular outerring 30 and interconnected web 40 may be made by injection orcompression molding, castable polymer, or any other method generallyknown in the art and may be formed at the same time so that theirattachment is formed by the material comprising the inner surface 20,outer ring 30 and interconnected web 40 cooling and setting.

As shown in FIG. 1, generally annular outer ring 30 may further have aradially external surface 34 to which a tread-carrying layer 70 isattached. Attachment may be done adhesively or using other methodscommonly available in the art. In addition, as seen in FIG. 11-13,tread-carrying layer 70 may comprise embedded reinforcing belts 72 toadd increased overall stiffness to non-pneumatic tire 10 wherein theembedding of the reinforcing belts 72 is accomplished according tomethods commonly available in the art. Reinforcing belts 72 may be madeof steel or other strengthening materials.

FIGS. 11-13 show several possible examples of the arrangement ofreinforcing belts 72 in tread-carrying layer 70. FIG. 11 is a prior artversion showing a tread 74 at a radial outermost portion of tire 10.Moving radially inwardly are a plurality of reinforcing belts 72 a, alayer of support material 76, and a second plurality of reinforcingbelts 72 b. In this embodiment, reinforcing belts 72 a, 72 b arearranged so that each belt is generally constant radial distance fromaxis of rotation 12.

Turning to the embodiment of FIG. 12, a tread-carrying layer 70 similarto that of FIG. 11 is shown. However, the embodiment of FIG. 12 showsthe layer of support material 76 being approximately bisected in agenerally radial direction by at least one transverse reinforcing belt72 c. Support material may be a rubber, polyurethane or similar compoundthat supports the changing loads generated by friction between footprintregion 32 and the ground and the torsional twisting of the rest oftread-carrying layer 70 caused by rotation of tire 10 about axis 12.

Tread-carrying layer 70 of FIG. 13 resembles that of FIG. 11 butcomprises two additional groupings of reinforcing belts 72. In additionto the generally radially constant plurality of reinforcing belts 72 a,72 b, tread-carrying layer 70 in FIG. 13 includes transverse reinforcingbelts 72 d, 72 e. Transverse reinforcing belts 72 d, 72 e include atleast one reinforcing belt 72 d proximate a longitudinally inner surfaceand at least one reinforcing belt 72 e proximate a longitudinally outersurface, such that reinforcing belts 72 a, 72 b, 72 d, 72 e generallyenclose layer of support material 76 in a generally rectangular boxshape.

Interconnected Web

Interconnected web 40 of non-pneumatic tire 10 connects generallyannular inner surface 20 to generally annular outer ring 30. Itcomprises at least two radially adjacent layers 56, 58 of web elements42 that define a plurality of generally polygonal openings 50. In otherwords, a slice through any radial portion of non-pneumatic tire 10extending from the axis of rotation 12 to the generally annular outerring 30 passes through or traverses at least two generally polygonalopenings 50. Generally polygonal openings 50 may assume various shapes,some of which are shown in FIGS. 4-10. In many embodiments, a majorityof generally polygonal openings 50 may be generally hexagonal. However,it is possible that each one of the plurality of generally polygonalopenings 50 has at least three sides. In one embodiment, the pluralityof generally polygonal openings 50 are either generally hexagonal inshape or hexagonal in shape circumferentially separated by openings thatare generally trapezoidal in shape, as can be seen in FIG. 1, givinginterconnected web 40 a shape that may resemble a honeycomb.

Interconnected web 40 may be designed such that one web element 42connects to generally annular inner surface 20 at any given point orline along generally annular inner surface such that there are a firstset of connections 41 along generally annular inner surface. Likewise,one web element 42 may connect to generally annular outer ring 30 at anygiven point or line along an internal surface 33 of generally annularouter ring such that there are a second set of connections 43 alonggenerally annular outer ring. However, more than one web element 42 mayconnect to either generally annular inner surface or to generallyannular outer ring at any given point or line.

As shown in FIGS. 4-10, interconnected web 40 further comprisesintersections 44 between web elements 42 in order to distribute appliedload, L, throughout interconnected web 40. In these embodiments, eachintersection 44 joins at least three web elements 42. However,intersections 44 may join more than three web elements 42, which mayassist in further distributing the stresses and strains experienced byweb elements 42.

Web elements 42 may be angled relative to a radial plane 16 containingthe axis of rotation 12 that also passes through web element 42. Byangling the web elements 42, applied load, L, which is generally appliedperpendicular to axis of rotation 12, may be eccentrically applied toweb elements 42. This may create a rotational or bending component of anapplied load on each element, facilitating buckling of those webelements 42 subjected to a compressive load. Similarly situated webelements 42 may all be angled by about the same amount and in the samedirection relative to radial planes 16. Preferably, however,circumferentially consecutive web elements 42, excluding tangential webelements 45, of a layer of plurality of generally polygonal openings 50are angled by about the same magnitude but measured in oppositedirections about radial planes such that web elements 42 are generallymirror images about radial plane 16 of one another.

Each of the openings within the plurality of generally polygonal tubularopenings 50 may, but is not required, to be similar in shape. FIG. 7,for example shows a first plurality of generally polygonal openings 50that is different in shape from a second plurality of generallypolygonal openings 51. In this embodiment, at least one opening of thefirst plurality of general polygonal openings 50 may be smaller than atleast one opening of the second plurality of generally polygonalopenings 51. FIG. 7 also shows that each generally polygonal opening inthe first plurality of generally polygonal openings 50 has an innerboundary 57 spaced a radial distance, R₁, from axis of rotation 12 andeach generally polygonal opening in the second plurality of generallypolygonal openings 51, has a second inner boundary 59 spaced a radialdistance, R₂, which may be greater than R₁, from axis of rotation 12.

As shown in FIGS. 7 & 8, openings in a radially inner layer 56 may besimilarly shaped as compared to those in a radially outer layer 58 butmay be sized differently from those openings such that the generallypolygonal openings 50 increase in size when moving from opening toopening in a radially outward direction. However, turning to FIG. 10, asecond plurality of generally polygonal openings 51 in a radially outerlayer 58 may also be smaller than those in a first plurality ofgenerally polygonal openings 50 in a radially inner layer 56. Inaddition, the second plurality of generally polygonal openings may beeither circumferentially separated from each other by a third pluralityof generally polygonal openings 53 or may be greater in number than thefirst plurality of generally polygonal openings 50, or it may be both.

FIGS. 1-9 show several variations of plurality of generally polygonalopenings 50 that are generally hexagonally shaped. As shown, theseopenings may be symmetrical in one direction or in two directions, orthey may not be symmetrical at all. For example, in FIG. 1, radialsymmetry planes 14 bisect several of the plurality of generallypolygonal openings 50. Those openings are generally symmetrical aboutradial symmetry planes 14. However, interconnected web 40 of tire 10 mayalso be generally symmetrical as a whole about radial symmetry planes.In comparison, second plurality of generally polygonal openings 14 maybe generally symmetrical about similar radial symmetry planes 14. Inaddition, as shown in FIGS. 7-8, a second plurality of generallypolygonal openings may be generally symmetrical about lines tangent to acylinder commonly centered with axis of rotation 12, providing a seconddegree of symmetry.

Web elements 42 may have significantly varying lengths from oneembodiment to another or within the same embodiment. For example,interconnected web 40 in FIG. 7 comprises web elements 42 that aregenerally shorter than web elements of the interconnected web shown inFIG. 6. As a result interconnected web 42 may appear more dense in FIG.7, with more web elements 42 and more generally polygonal openings 50 ina given arc of tire 10. In comparison, FIGS. 9 and 10 both showinterconnected webs 40 which web elements 42 substantially vary inlength within the same interconnected web. In FIG. 9, radially inwardweb elements 42 are generally shorter than web elements 42 locatedcomparatively radially outward. However, FIG. 10 shows radially inwardweb elements 42 that are substantially longer than its radially outwardweb elements 42. As a result, interconnected web 40 of FIG. 9 appearsmore inwardly dense than interconnected web 42 of FIG. 10.

Remaining with FIG. 10, an interconnected web 40 is shown such that webelements 42 define a radially inner layer 56 of generally polygonalopenings 50 that is significantly larger than a radially outer layer 58of generally polygonal openings 50. Radially inner layer 56 may comprisealternating wedge-shaped openings 55 that may or may not be similarlyshaped. As shown, second plurality of generally polygonal openings 51may be separated from first plurality of generally polygonal openings 50by a generally continuous web element 42 of interconnected web 40 spacedat a generally constant radial distance from axis of rotation 12.Generally continuous, generally constant web element 42 may assist inproviding further stiffness to non-pneumatic tire 10 in regions that areresistant to deformation.

The combination of the geometry of interconnected web 40 and thematerial chosen in interconnected web 40 may enable an applied load, L,to be distributed throughout the web elements 42. Because web elements42 are relatively thin and may be made of a material that is relativelyweak in compression, those elements 42 that are subjected to compressiveforces may have a tendency to buckle. These are the elements that aregenerally between the applied load, L, that generally passes throughaxis of rotation 12 and footprint region 32 and are represented asbuckled section 48 in FIG. 2.

When buckling occurs, the remaining web elements 42 may experience atensile force. It is these web elements 42 that support load, L.Although relatively thin, because web elements 42 may have a hightensile modulus, E, they may have a smaller tendency to deform butinstead may help maintain the shape of generally annular outer ring 30.

Although generally annular inner surface 20, generally annular outerring 30, and interconnected web 40 may be comprised of the samematerial, they may all have different thicknesses. Generally annularinner surface may have a first thickness, t_(i), generally annular outersurface may have a second thickness, t_(o), and interconnected web mayhave a third thickness, t_(e). As shown in FIG. 1, first thickness t_(i)may be less than second thickness t_(o). However, third thickness,t_(o), may be less than either first thickness t_(i), or secondthickness, t_(o). This is preferred as a thinner web element 42 bucklesmore easily when subjected to a compressive force whereas a relativelythicker generally annular inner ring 20 and generally annular outersurface 30 may help maintain lateral stiffness of non-pneumatic tire 10in an unbuckled region by better resisting deformation.

Thickness, t_(e), of web elements 42 may vary, depending onpredetermined load capability requirements. As the applied load, L,increases, web elements 42 may increase in thickness, t_(o), to provideincreased tensile strength, reducing the size of the openings in theplurality of generally polygonal openings 50. However, thickness, t_(e),should not increase too much so as to inhibit buckling of those webelements 42 subject to a compressive load. As with choice of material,thickness, t_(o), may increase significantly with increases in appliedload, L.

In addition to web elements 42 that are angled relative to radial planes16 passing through axis of rotation 12, interconnected web 40 may alsoinclude tangential web elements 45, as shown in FIGS. 1-9. Tangentialweb elements 45 are oriented such that they are generally aligned withtangents to cylinders or circles centered at axis of rotation 12.Tangential web elements 45 are preferred because they assist indistributing applied load, L. When applied load, L, is applied, webelements 42 in a region above axis of rotation 12 are subjected to atensile force. Without tangential web elements 45, interconnected web 40may try to deform by having the other web elements 42 straighten out,orienting themselves in a generally radial direction, resulting instress concentrations in localized areas. However, by being oriented ina generally tangential direction, tangential web elements 45 distributeapplied load, L, throughout the rest of interconnected web 40, therebyminimizing stress concentrations.

Staying with FIGS. 1-9 a plurality of generally polygonal openings 50are shown wherein each one of said plurality of generally polygonalopenings 50 is radially oriented. Generally polygonal openings may beoriented such that they are symmetrical about radial symmetry planes 14that pass through axis of rotation 12. This may facilitate installationby allowing tire 10 to still function properly even if it is installedbackwards because it should behave in the same manner regardless of itsinstalled orientation.

Interconnected web 40, generally annular inner surface 20 and generallyannular outer ring 30 may be molded all at once to yield a product thathas a width or depth of the finished non-pneumatic tire. However,interconnected web 40, generally annular inner surface 20 and generallyannular outer ring 30 may be manufactured in steps and then assembled asseen in the embodiments of FIGS. 14-16. In these figures, each segment18 has an interconnected web 40 having the same pattern as thenon-pneumatic tire 10 of FIG. 1.

FIG. 14 shows a perspective view where tire 10 comprises a plurality ofsegments 18. Segments 18 may have a generally uniform width, W, but theymay also have different widths. Segments 18 may be made from the samemold so as to yield generally identical interconnected webs 40, but theymay also be made from different molds to yield varying patterns ofinterconnected webs 40. In addition, as seen in FIGS. 14 and 15,segments 18 may be circumferentially offset from one another so that aplurality of generally polygonal openings 50 a of one segment 18 is notgenerally aligned with a plurality of similarly-shaped generallypolygonal openings 50 b of a radially adjacent segment 19. The segmentsmay or may not alternate so that every other segment 18 is generallyaligned. FIG. 15 shows an embodiment having seven segments 18, where thefirst, third, fifth and seventh segments 18 a, 18 c, 18 e and 18 g aregenerally aligned with each other, the second, fourth and six segments18 b, 18 d, and 18 f are generally aligned with each other, but the twogroups of segments are not generally aligned as a whole. In addition,FIG. 16 is a cutaway view showing two radially adjacent segments 18, 19that are not generally aligned. This stacking orientation may help withbuckling around footprint region 32, may decrease vibration and noise,and may provide greater torsional stiffness to non-pneumatic tire 10.

The choice of materials used for interconnected web 40 may be animportant consideration. The material that is used should buckle easilyin compression, but be capable of supporting the required load intension. Preferably, interconnected web is made of a cross-linked oruncross-linked polymer, such as a thermoplastic elastomer, athermoplastic urethane, or a thermoplastic vulcanizate. More generally,in one embodiment, the interconnected web 40 may preferably be made of arelatively hard material having a Durometer measurement of about 40 Dwith a high tensile modulus, E, of about 21 MPa or about 3050 psi.However, tensile modulus may vary significantly for rubber or otherelastomeric materials, so this is a very general approximation. Inaddition, Durometer and tensile modulus requirements may vary greatlywith load capability requirements.

Other advantages may be obtained when using a polymer material such aspolyurethane to make non-pneumatic tire 10 instead of the rubber oftraditional tires. A manufacturer of the claimed invention may only needa fraction of the square footage of work space and capital investmentrequired to make rubber tires. The amount of skilled labor necessary maybe significantly less than that of a rubber tire plant. In addition,waste produced by manufacturing components from a polyurethane materialmay substantially less than when using rubber. This is also reflected inthe comparative cleanliness of polyurethane plants, allowing them to bebuilt in cities without the need for isolation, so shipping costs may becut down. Furthermore, products made of polyurethane may be more easilyrecyclable.

Cross-linked and uncross-linked polymers, including polyurethane andother similar non-rubber elastomeric materials may operate at coolertemperatures, resulting in less wear and an extended fatigue life oftire 10. In addition, the choice of materials for interconnected web 40and outer ring 30 may significantly decrease rolling resistance, leadingto about a 10% decrease in fuel consumption. Polyurethane has betterabrasion resistance and, therefore, better tread wear than a traditionalrubber tire and, unlike rubber, it is inert, making it resistant tooxidization or reaction with other materials that make rubber harden oreven crack.

In another embodiment shown in FIGS. 17 & 18, the interconnected web 40comprises web elements 42 that also contain strengthening components 46such as carbon fibers, KEVLAR®, or some additional strengtheningmaterial to provide additional tensile strength to the interconnectedweb 40. Properties of strengthening components 46 may be high strengthin tension, low strength in compression, light weight, good fatigue lifeand an ability to bond to the material comprising interconnected web 40.

In an additional embodiment, interconnected web 40 may be directlyengaged by hub 60, tread-carrying layer 70 or both. For example, hub 60and tread-carrying layer 70 may either or both comprise dovetail joints.Hub 60 and tread-carrying layer 70 may then be inserted into a mold withthe material comprising interconnected web filling the joints. In thiscase, radially external surface 62 of hub 60 comprises generally annularinner surface 20 and a radially internal surface 78 of tread-carryinglayer 70 comprises generally annular outer ring 30. Therefore, wheninterconnected web 40 sets, the interconnected web is directly engaged,obviating the need to bond or otherwise affix interconnected web 40 togenerally annular outer ring 30, for example.

EXAMPLE

In one embodiment, a non-pneumatic tire 10 possesses the interconnectedweb 40 of the configuration shown in FIGS. 1 & 2. Tire 10 has a radiusof about 9.5 inches and hub 60 has a radius of about 4⅜ inches.

In general, the force required for buckling of a column is governed bythe equation: F buckling=(KEIn^2)/1^2 where K=a constant whose valuedepends on how the ends of the column are affixed, E=tensile modulus,I=the area moment of inertia, and l=the unsupported length of thecolumn.

If each web element 42 of interconnected web 40 is modeled as its ownthin column, the radially innermost elements will be fixed at one endand free to move laterally at another end. In this instance, K=¼.

In this example, interconnected web 40 and generally annular outer ring30 are made of a similar material having a tensile modulus, E, of about21 MPa or 3050 psi.

Tire 10 may be about 8 inches wide and each web element 42 ofinterconnected web 40 may be between about 0.04 inch and 0.1 inch thick.A thickness of about 0.08 inch will be used for this example. In thiscase, the area moment of inertia, I=(w*h^3)/12 where w=the width of eachweb element 42, 8 inches and h=the thickness, 0.08 inch. Therefore, I isabout 0.000341 in^4.

Using the tire and hub radii mentioned above, and observing the patternof interconnected web 40 as seen in FIGS. 1 & 2, each web element 42 mayhave an approximate length of about (9.5″-4.375″)/4, or approximately1.28 inch.

Based on these numbers, F_buckling=(KEIn^2)/1^2=about 1.59 lbs. Inaddition, web elements 42 of interconnected web 40 are angled withrespect to a radial direction to facilitate buckling, which may furtherdecrease F_buckling.

In this application, non-pneumatic tire 10 is subjected to a load, L, ofabout 250 lbs. Load, L, is distributed throughout web elements 42 suchthat the entire load, L, is not borne by a single web element, 42.However, the web elements 42 most directly aligned with the direction ofload, L, should bear the greatest portion of the load. Since L issignificantly larger than F_buckling, elements 42 of interconnected web40 that are subjected to a compressive force will buckle and not supportload, L.

While the foregoing written description of the invention enables one ofordinary skill to make and use what is considered presently to be thebest mode thereof, those of ordinary skill will understand andappreciate the existence of variations, combinations, and equivalents ofthe specific exemplary embodiment and method herein. The inventionshould therefore not be limited by the above described embodiment andmethod, but by all embodiments and methods within the scope and spiritof the invention as claimed.

What is claimed is:
 1. A non-pneumatic tire comprising: a generallyannular inner surface that attaches to a hub, a generally annular outerring, an interconnected web between said generally annular inner surfaceand said generally annular outer ring and defining a plurality ofgenerally polygonal openings, an axis of rotation; and a tread layercoupled to a radially external surface of the outer ring and comprising:a first axially-extending reinforcing belt extending generally parallelto the axis of rotation and coupled to the outer ring; a secondaxially-extending reinforcing belt extending generally parallel to theaxis of rotation and spaced apart from the first axially-extendingreinforcing belt; at least one radially-extending reinforcing beltextending in a generally radial direction and generally perpendicularlyto the first and second axially-extending reinforcing belts; and asupport material positioned generally between the firstaxially-extending reinforcing belt and the second axially-extendingreinforcing belt.
 2. A non-pneumatic tire comprising: a generallyannular inner surface that attaches to a hub, a generally annular outerring, an interconnected web between said generally annular inner surfaceand said generally annular outer ring, an axis of rotation; and a treadlayer coupled to the outer ring and comprising: a firstaxially-extending reinforcing belt extending generally parallel to theaxis of rotation and having a first end and a second end; a secondaxially-extending reinforcing belt extending generally parallel to thefirst axially-extending reinforcing belt and spaced apart therefrom, thesecond axially-extending reinforcing belt having a first end and asecond end; a first radially-extending reinforcing belt extending in agenerally radial direction and generally perpendicularly to the firstand second axially-extending reinforcing belts, the firstradially-extending reinforcing belt having a first end coupled to thefirst end of the first axially-extending reinforcing belt and a secondend coupled to the first end of the second axially-extending reinforcingbelt; a second radially-extending reinforcing belt extending in agenerally radial direction and spaced apart from the firstradially-extending reinforcing belt, the second radially-extendingreinforcing belt being generally perpendicular to the first and secondaxially-extending reinforcing belts, the second radially-extendingreinforcing belt having a first end coupled to the second end of thefirst axially-extending reinforcing belt and a second end coupled to thesecond end of the second axially-extending reinforcing belt, and thefirst axially-extending reinforcing belt, the second axially-extendingreinforcing belt, the first radially-extending reinforcing belt, and thesecond radially-extending reinforcing belt cooperating with each otherto define a rectangular opening within the tread layer; and a supportmaterial positioned within the rectangular opening.
 3. A non-pneumatictire according to claim 2, wherein said interconnected web defines aplurality of generally hexagonally shaped openings circumferentiallyspaced around said tire and radially spaced at varying distances fromsaid axis of rotation, a first plurality of generallyquadrilaterally-shaped openings adjacent said generally annular innersurface and a second plurality of generally quadrilaterally-shapedopenings adjacent said generally annular outer ring, each of said firstplurality of generally quadrilaterally-shaped openings and each of saidsecond plurality of generally quadrilaterally-shaped openingscircumferentially separated from each other of said first plurality ofgenerally quadrilaterally-shaped openings and each other of said secondplurality of generally quadrilaterally-shaped openings, respectively, byat least one of said plurality of hexagonally shaped openings, so as tosupport a load by working in tension.
 4. The non-pneumatic tire of claim1, wherein at least half of the generally polygonal openings arehexagonally shaped.
 5. The non-pneumatic tire according to claim 1,wherein a substantial amount of said load is supported by a plurality ofthe web elements working in tension.
 6. The non-pneumatic tire accordingto claim 1, wherein said plurality of generally polygonal openingscomprises a first plurality of generally polygonal openings having afirst shape and a second plurality of generally polygonal openingshaving a second shape different from said first shape.
 7. Thenon-pneumatic tire according to claim 6, wherein at least one of saidfirst plurality of generally polygonal openings and at least one of saidsecond plurality of generally polygonal openings are traversed whenmoving in any radially outward direction from said axis of rotation. 8.The non-pneumatic tire according to claim 6, wherein each of said firstplurality of generally polygonal openings has a first inner boundaryspaced at a first radial distance and each of said second plurality ofgenerally polygonal openings has a second inner boundary spaced at asecond, greater radial distance.
 9. The non-pneumatic tire according toclaim 8, wherein at least one generally polygonal opening of said firstplurality of generally polygonal openings is larger than at least onegenerally polygonal opening of said second plurality of generallypolygonal openings.
 10. The non-pneumatic tire according to claim 1,wherein one radial web element engages said inner surface at a givenlocation.
 11. The non-pneumatic tire according to claim 1, wherein oneradial web element engages said outer ring at a given location.
 12. Thenon-pneumatic tire according to claim 1, wherein said interconnected webcomprises intersections between said web elements, said intersectionsjoining at least three web elements.
 13. The non-pneumatic tireaccording to claim 1, wherein said generally annular inner surface has afirst thickness, said generally annular outer ring has a secondthickness, and said web elements have a third thickness, said thirdthickness being smaller than said first thickness or said secondthickness.
 14. The non-pneumatic tire according to claim 1, wherein eachone of said plurality of generally polygonal openings is radiallyoriented.
 15. The non-pneumatic tire according to claim 1, wherein eachone of said plurality of generally polygonal openings has at least threesides.
 16. The non-pneumatic tire according to claim 1, wherein saidplurality of generally polygonal openings are generally hexagonallyshaped.
 17. The non-pneumatic tire according to claim 1, furthercomprising a plurality of joined segments each having a width narrowerthan a width of said tire.
 18. The non-pneumatic tire according to claim17, wherein a first joined segment is circumferentially offset from anadjoining segment.
 19. The non-pneumatic tire according to claim 17,wherein a first joined segment has an interconnected web that is amirror image of an interconnected web of a second joined segment. 20.The non-pneumatic tire according to claim 1, wherein a radially innerlayer of said plurality of generally polygonal openings comprisesalternating generally wedge-shaped openings.
 21. The non-pneumatic tireaccording to claim 1, wherein each one of said plurality of generallypolygonal openings is generally symmetrical about a radial symmetryplane.
 22. The non-pneumatic tire according to claim 1, wherein saidinterconnected web comprises a generally continuous, radially orientedradial web element intermediate said generally annular inner surface andsaid generally annular outer ring.
 23. The non-pneumatic tire accordingto claim 1, wherein said generally annular inner surface is adhesivelyengaged with said hub.
 24. The non-pneumatic tire according to claim 1,wherein said generally annular inner surface is chemically bonded tosaid hub.
 25. The non-pneumatic tire according to claim 1, wherein saidinterconnected web is made of a polymer.
 26. The non-pneumatic tireaccording to claim 1, wherein said web elements comprise additionalstrengthening components.
 27. The non-pneumatic tire according to claim1, wherein a plurality of said radial web elements are angled relativeto a plane containing said axis of rotation to facilitate buckling ofsaid radial web elements.
 28. The non-pneumatic tire according to claim27, wherein the support material is comprised of at least one of rubberand polyurethane.